The present invention relates to a power switch circuit for a remote controlled electronic equipment such as a television receiver.
Referring to FIG. 1, a circuit diagram of a prior art power switch circuit for a remote controlled electronic equipment is shown.
In FIG. 1, a power from a commercial A.C. power supply 1 is fed to a control unit 7 for controlling turn-on and turn-off of a relay 3 which is used as an automatic switch, through a manual switch 2, and also fed to a load circuit 5 of the electronic equipment through a make contact 3' of the relay 3. The control unit 7 is put in an operating condition upon turn-on of the manual switch 2. A remote control unit 6 generates an ultrasonic signal which is received by the control unit 7 to control turn-on and turn-off of the relay 3.
In response to the ultrasonic signal (turn-on control signal) from the remote control unit 6, the control unit 7 causes an excitation current to flow through a winding 4 of the relay 3 to turn on or close the make contact 3' so that the excitation current continues to flow through the winding 4 even after the termination of the reception of the ultrasonic signal. When the control unit 7 receives another ultrasonic signal (turn-off control signal or stop signal), it causes the excitation current to be terminated to turn off the make contact 3' so that the relay 3 is kept in its off state even after the termination of the ultrasonic signal. Thus, the control unit 7 serves to alternately switch the relay 3 between its on-state and its off-state.
Since such control unit 7 is required to hold the on or off state of the relay 3 to which it was switched by the ultrasonic signal, the control unit 7 has included a hold means such as a bistable flip-flop.
Furthermore, the control unit 7 includes a complex erroneous operation prevention circuit in order to prevent erroneous operation from occurring due to a spurious ultrasonic signal which may be an ultrasonic signal generated by the strike of keys or coins or an ultrasonic signal generated from telephone ringing. In order to prevent the relay 3 from being turned on by such spurious ultrasonic signal or a malfunction of the control unit 7 once the relay 3 has been turned off by an ultrasonic signal, a manual operation has been required to turn off the manual switch 2.
It is an object of the present invention to provide a power switch circuit for a remote controlled electronic equipment which has overcome the drawbacks of the prior art and which assures the holding of power switch circuit in its off-state by a remote control operation.
It is another object of the present invention to provide a power switch circuit for a remote controlled electronic equipment in which a control unit for controlling the turn-on and turn-off of an automatic switch is turned on by a manual operation and turned off by a remote control turn-off signal.